In securing a boat to a dock, attention must be given to protecting the boat against abrasion from repeatedly colliding with the dock structure under a combination of wind and wave action. Even under calm conditions, passing boats can produce waves that jostle the boat against anything close to it. The problem exists primarily when the boat is secured at one side only, as the usual marina slip permits dock lines at both sides that can center the boat in the slip clear of danger. The adjacent dock structure is usually one of two types: planar vertical surfaces, or spaced cylindrical pilings. A so-called "fender" has come into almost universal use as a cushion to be interposed between the boat and the possible sources of damage. Both lateral and vertical movement of the boat against the dock must be considered. Carefully placed spring lines will usually minimize fore-aft movement.
Placement of the fenders is something of an art. These generally cylindrical cushions can be from a foot to three feet long, and from four inches to a foot in diameter. Usually, a short line extends from one or both ends of the fender to be tied to some convenient part of the boat to place the fender in the desired position. Opposite a piling, the fender is usually placed horizontally; and against a broad vertical surface, it is usually vertical. Fenders can be tied to deck cleats, or to the safety rails usually installed around the periphery of the deck. The present invention is associated with the latter arrangement. It has also been found useful as a storage hanger for coiled and shanked dock lines, and for securing throwable life preservers that must be freed quickly for use.